#include <QCoreApplication>
#include <iostream>
#include <math.h>

using namespace std;
int main(void)
{
int N;
double F;

char key;
cout<< "N=";
cin>> N;
cin.get(key);
F=1;
while (N > 1)
{ F*=N; N-=2; }

cout << "Otvet = "<< F << endl;;
cout << "Press key";

cin.get(key);
return 0;
}

